Magnetic resonance imaging (MRI) systems use a strong, homogenous magnetic field to acquire images of a patient. The strength of the magnetic field is typically greater than about 0.5 Tesla, and in many applications can be as high as about three Tesla.
Magnets that produce strong magnetic fields, such as those magnets employed in an MRI system, can also produce a fringe magnetic field that extends beyond the physical confines of the magnet itself. This fringe magnetic field is unwanted, as it attracts ferromagnetic objects, interferes with sensitive electronic equipment and erases data from magnetic storage media.
Most magnets employed in an MRI system are designed to be large enough to accommodate adult-sized patients. However, the larger the magnet, the larger the fringe magnetic field produced.
Newborn babies, also known as neonates, having a medical condition, are placed in specially designed incubators to aid in their development and recovery. These incubators provide a controlled environment for the neonate wherein environmental factors such as temperature, humidity and oxygenation of the atmosphere are regulated. These incubators also commonly have equipment for monitoring the vital functions of the neonate.
Challenges in neonatal care arise when MRI scans of a neonate are needed. In particular, the monitoring equipment in the incubators can be affected by the fringe magnetic field. Further, the fragile nature of the neonates makes them sensitive to movement or handling, beyond that which is necessary, and typically carried out by trained medical personnel who specialize in the particular needs of neonates.
With regard to the fringe magnetic field, some MRI magnet designs employ a set of superconducting coils, separate from the main superconducting coils of the magnet, to actively screen the fringe magnetic field. These screening coils are disposed concentrically and co-axially with the main coils, and are connected to each other in series opposition. The effect of the screening coils is to reduce the strength of the fringe magnetic field.
Even with active screening, there remains a significant fringe magnetic field within certain distances from the magnet center. For example, with a typical MRI magnet having active screening, a fringe magnetic field having a strength of five Gauss can still exist at a distance of as much as 4.5 meters from the magnet center.
Because of the effect the fringe magnetic field has on the neonate monitoring equipment, MRI systems typically are not located within neonatal units. Further, the dimensions and weight of an MRI system typically require that the system be centrally located in a hospital for use by a number of different units. For example, typical MRI magnets are designed with a warm-bore of between about 50 centimeters to about 110 centimeters, e.g., about 90 centimeters, and an overall physical size of nearly 1.5 to two meters in diameter, 1.5 to two meters in length and a weight of four to ten tons.
As a result, MRI systems are generally located within a separate imaging suite and the neonates are transported from the neonatal unit to the imaging suite for scanning. To help minimize the amount of trauma this transporting causes, special incubators have been created to allow the neonate to remain in a controlled environment during transportation and imaging. These special incubators have monitoring equipment that is not affected by a magnetic field.
However, the neonates must still be transferred from their regular incubator to the special incubator, transported to/from the MRI system and then returned to their regular incubator. Thus, this procedure involves extensive movement of the neonate, which can be detrimental to recovery. Further, the special incubator is typically smaller than a regular incubator, which can be restrictive and cause stress for the neonate. Also, any other equipment that accompanies the neonate, such as resuscitation equipment, must also be transported. Therefore, frequent and repeated imagings using this procedure are logistically difficult to arrange.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for improved techniques for obtaining MRI images of neonates.